Push button electric switch



Aug. 19, 1952 s, SNELL 2,607,871

PUSH BUTTON ELECTRIC SWITCH Filed June 15, 1951 5 Shets-Sheet 1 2/ 2/ I I I I l I I /2 I o /4 [2 X r /3- F N 2/ o 22 I 23 I lll fi fi" I ll 25 r I4 29 2 :l T F050 20 24 26';

/ E if r 1 E j lqvemvr v FI Eo lo M urice $810" SIM By I M+M Attorneys Aug. 19, 1952 SNEL 2,607,871

PUSH BUTTON ELECTRIC SWITCH Filed June 15; 1951 5 Sheets-Sheet 2 2 19* J6 l2 /2 Q l Inventor Maurice 8a an Snell By M4 Attorneys Aug. 19, 1952 I M. s. SNELL 2,607,871

PUSH BUTTON ELECTRIC SWITCH Filed June 15, 1951 5 Sheets-Sheet 3 lnvemor Maui-(be Saxon 5nd! 8) W M$W Attorneys Patented Aug. 19, 1952 PUSH BUTTON ELECTRIC SWITCH Maurice S. Snell, Suttons Mill, Cranham ling land, assignor to Dowty Equipment Limited, Clieltenham, England Application June 15, 1951, Serial No. 231,631 In Great Britain March 14, 1951 Claims. 1

When a push button electric switch is used in some control s stems it is desirable to provide locking mechanism for preventing operation of the switch under certain circumstances, the locking mechanism usually being controlled electro'magneticallyr In some such systems it may nevertheless be desirable also to arrange for the switch to be capable of being operated despite the locking action of locking mechanism associated with the switch. An example of such a condition is that of a push button switch used to control retraction of an aircraft undercarriage. It will be understood that in the normal course of events it is desirable to prevent anyone from effecting retraction of the undercarriage while the aircraft is grounded, and for this reason locking mechanism is associated with the switch. Although this provision is highly desirable in all normal circumstances, it is well recognized that there may arise a circumstance when retraction of the undercarriage is necessary even though the aircraft is grounded. Thus during take-oft it may happen that owing to an obstruction appearing, or for some other reason, the pilot may wishto bring his machine to rest as quickly as possible, and this he can achieve by retracting the undercarriage and allowing the aircraft to distribute its weight over a larger surface of the runway, thereby creating additional friction. The fact that parts of the aircraft may be damaged is considered to be of secondary importance. The push button switch controlling retraction of the undercarriage would therefore have to include provision for permitting the switch to be operated despite the fact that the locking mechanism is in its locking position, and the object of the present invention is to provide means whereby this can be achieved.

Broadly stated, the present invention consists in a push button electric switch having associated locliing mechanism for preventing normal operation of the switch under certain circumstances, and having means whereby the button, when locked, can be operated in an emergency, said button being movable from an outer position to an inner or depressed position to actuate the switch, and is characterized in that the button engages the locking element of the locking mechanism through a rod-like member extending between the locking element and an inner surface of the button, and in that the button is guided for turning movement whereby the button can be turned from its normal position to bring a hollow or cut-away portion of the button into register with the rod-like member to permit depression of the button despite the locking action of the locking element.

The arrangement is preferably such that when the button is depressed for emergency operation of the switch, the button and rod-like member so engage one another that they move together during outward movement of the button, the rod-like member then serving to prevent the button from turning back to its normal angular position. With such an arrangement the button may be formed with a keyhole or equivalent communication with the hollow or cut-away portion of the button so that a key or other implement can be inserted to return the rod-like member after emergency operation of the button.

The preferred embodiment of the invention will now be described with reference to the accompanying drawings, of. which:

Figure 1 is a sectional elevation;

Figure 2 is a corresponding plan view, and

Figures 3, 4 and 5 are part sectional elevations showing different positions occupied by parts during emergency operation of the switch.

As shown, a push button indicated generally at H carries a pair of moving contacts 12 which, by depression of the button, are brought into engagement with a corresponding pair of fixed contacts I3 mounted in an insulated casing Id. The button I I comprises an upper part 15, in the nature of a sleeve or other rotative element, and a lower part l6, which constitutes the support for contact elements I2. Both parts are guided for axial movement of the button as a whole, and

.the upper part or sleeve I5 is also guided for turning movement about the axis of the button. being journalled about the upper end of a stem ll of the lower part [5. A spring l8 fixed at one end 19 to the lower part It and at the upper end 20 to the sleeve I5 biases the sleeve so that the latter tends to assume what may be termed a normal angular position determined by stops (not shown). The normal angular position of the sleeve is shown in Figure 1. The sleeve carries in addition to the push button proper a pair of upstanding pins 2| by means of which the sleeve can be turned from its normal angular position about the stem ii, in opposition to the torsional force of the spring I8, tending to return it to and hold it in that normal angular position.

A rod-like member 22 terminating at its lower end in a tube 23 extends down through a guide in the lower part I6 of the button, and its tube 23 extends over the upper end of a fixed stem 24 in the casing Id. The stem 24 has an annular channel 25 constituting a shoulder which re- 3 ceives a transverse locking element or dog 26, which latter extends beneath the tube 23 of the rod-like member 22 except when the locking dog 26 is withdrawn out of the path of the tube 23 by energization of an electro-magnet 21. So long as the electro-magnet 21 is energized the switch is free to be operated simply by pressure applied on the upper end or sleeve of the button I l. The button as a whole will then move down into the casing l4 and bring the moving contacts 82 into engagement with the fixed contacts l3, and the tube 23 of the rod-like member 22 will pass downwardly over the fixed stem 24 without hindrance. All the while the electro-magnet 21 is de-energized the transverse locking dog 28 carried by the armature of the electro-magnet will prevent full downward movement of the rodlike member 22 and will thus prevent downward movement of the push button H and closure of the circuit through the contacts l2, l3. If, despite the locking action of the locking element 26, it is desired to operate the switch contacts, the upper part or sleeve of the push button can be turned through 90 degrees in a clockwise direction, as seen in Figure 2, to bring a bore 28 in the sleeve into register with the rod-like member 22. The button as a whole can then be depressed by the bore ZB-passing down over the rod-like member 22, notwithstanding that the latter is held up by the locking element 28, see

Figures 3 and 4. When the sleeve l5 has been turned and the push button H depressed to effect emergency operation of the switch, as in Figure 4, frictional engagement between the rodlike member 22 and the bore 28 is such that when the button is released and caused to return to its outer position, as seen in Figure 5, the rodlike member 22 moves out with the button to prevent the sleeve [5 from turning back to its normal angular position seen in Figure 1. There is thus given an indication that the switch has been operated in an emergency. In order that the rod-like member 22 may be returned from the position shown in Figure 5 to its normal position shown in Figure l, the push button proper of the button II is formed with a small aperture 29 disposed directly above the bore 28 so that by inserting a pin through the aperture 29 the rod-like member 22 can be pushed down out of the bore 28 in the sleeve I5. If desired the aperture 29 may be specially shaped to receive a correspondingly shaped key.

While it may be immaterial to the understanding of the switch and its operation as a switch, it may help in understanding the invention generally to know the circumstances in which the switch functions normally, or in an emergency The electromagnet 21 is arranged to be energized automatically as soon as and so long as the aircraft is airborne rather than ground-borne, and conversely, the electromagnet is automatically deenergized as soon as and so long as the aircraft is ground-borne. Connections, in known manner, to the alighting'mechanism accomplish this. Closure of a circuit at l2, l3 is-required to effect retraction of the undercarriage. Since such closure is mechanically impossible by the normal act of merely pressing inwardly on the button I I so long as the aircraft is ground borne. due to the intervention of the locking dog 26, but is possible as the aircraft becomes airborne, the normal operation, or prevention of operation, serves to effect or to prevent retraction, respectively, in normal circumstances. The emergency 4 operation, requiring turning of the sleeve [5 from its normal position in advance of its depression, permits retraction in an emergency even while ground-borne, notwithstanding the normal lock against retraction.

I claim:

1. A push button electric switch comprising two complemental contactelements, one whereof is movable towards and from operative contact with the other, a push button including a support whereon said movable contact is mounted and a sleeve mounted upon and for rotation about said support, and normally positioned in a normal angular position relative to the support, but rotatable from that position, means guiding said support and its supported sleeve for linear movement in a definite path towards and from contact-closed position, a pressure-transmitting element separate from but supported by said support with one end in position for engagement by said sleeve and depression thereby upon linear contact-closing movement of the sleeve, locking means independently controlled and positioned to engage and prevent depression of said pressure-transmitting element under certain normal conditions, and so to prevent contact between the complemental contact elements, the sleeve having a recess so located that, in the normal angular position of the sleeve the recess is out of alignment with said pressure-transmitting element, but by rotation of the sleeve from such normal angular position the recess may be aligned with and receive the cooperating end of the pressure-transmitting element upon contactclosing linear depression of the push button as a whole, and so the contact elements may be contacted in an emergency notwithstanding the interposition of the locking means to prevent normal depression of the pressure-transmitting element.

2. A push button electric switch as in claim 1, including spring means reacting between the sleeve and its support to retain the sleeve normally in and to return it to its normal angular position relative to the support, but yieldable for rotation of the sleeve to its emergency operating position.

3. A push button electric switch as in claim 1, wherein the pressure-transmitting element is formed generally as a rod extending generally parallel to but offset from the axis of rotation of the sleeve, with its one end located to be engaged by the end of the sleeve, and the recess formed in such end of the sleeve, similarly parallel to but ofiset from the sleeves axis of rotation.

4. A push button electric switch as in claim 3, wherein the rods end fits snugly within and frictionally engages the walls of the sleeves 1'61 cess, to withdraw with the sleeve as the push button is withdrawn from contact-closing position,

and by its continued engagement within the recess preventing rotation of the sleeve relative to the support back to its normal angular position until the rod is removed from the recess.

5. A push button electric switch as in claim 4, wherein the outer end of the sleeve is provided with a hole aligned with the sleeves recess, for the insertion of an implement wherewith to push the rods end from the sleeves recess.

MAURICE S. SNELL.

No references cited. 

